Energy tester for testing blasting machines that detonate electro-explosive devices

ABSTRACT

An apparatus for testing the energy output of a blasting machine used for detonating electro-explosive devices to determine if the blasting machine will supply sufficient energy to detonate the electro-explosive devices. The tester is capable of determining within plus or minus one Joule the output of a 25 Joule blasting machine. The energy tester includes go and no-go indicator lights to inform the operator of the blasting machine whether or not he has sufficient energy.

United States Patent Thakore 1 Nov. 25, 1975 1 ENERGY TESTER FOR TESTING 3 584 294 6/1971 Siwko H 124 1 ll 3,787,767 H1974 Hammer et 21!. 324/l58 R BLASTING MACHINES THAT DETONATE ELECTRO-EXPLOSIVE DEVICES {75] lnventor: Kaushik H. Thakore, Sidney, NY. Primary ExaminerR. V. Rolinec Assistant ExaminerErnest F. Karlsen "I H r l Assignee. 'rglhizlfendlx Corporation, Southfield, Attorney Agent or Firm RaymOnd l Elmer [22} Filed: Feb. 21, 1974 [21! App]. No.: 444,212 {57] ABSTRACT Related Applimtion Data An apparatus for testing the energy output of a blastl l Division Of 58F 1972 ing machine used for detonating electro-explosive de- 3365328 vices to determine if the blasting machine will supply q sufficient energy to detonate the electro-explosive de- 4 324/111; 324/!02 vices. The tester is capable of determining within plus [51] 601R 21/00 or minus one Joule the output of a 25 Joule blasting [58) F'eld Search 324/111 machine. The energy tester includes g0 and no-go in dicator lights to inform the operator of the blasting [561 Reierences cued machine whether or not he has sufficient energy.

UNITED STATES PATENTS 3179803 4/1965 Pychlau et al 4. 324/l ll 3 Claims, 4 Drawing Figures R'FEfiEA/CE SIG AL 65M A C TR/LLER MONOSTAELE 4 5 6 y CIRCUIT Mal TIM/MAM G0 0 amsrwa Q g 2 MACH/NF (amp/12,410 4 T 4 0 0 wan 41. A 5 0 60 R GEA/R/ITOR U.S. Patent Nov. 25, 1975 FIG! RfFERE/VCE SIG/VAL GEM Sheet 1 of 2 A c TR/LLER MONOSTABLf A g 8 4/ CIRCUIT Mot TlV/fiR/Ifid G0 5) BLAST/N6 g g MACH/IVE comm/@4101? T w o s/a/mL A 5 D 60 GENERATOR FIG. 4

CQMPARATOR 1 Mo/vosmazi our/ ur 5 ENERGY TESTER FOR TESTING BLASTING MACHINES TIIAT DETONATE ELECTRO-EXPLOSIVE DEVICES This is a division of application Ser. No. 317,911, filed Dec. 26, 1972, now U.S. Pat. No. 3,865,028.

BACKGROUND OF THE INVENTION This invention relates to blasting machines for detonating blasting caps, electro-explosive devices, or the like. The invention is more particularly related to capacitor discharge type blasting machines and an apparatus for determining when they are operating properly.

Basically, blasting devices for firing explosive devices include a source of power such as a battery, an oscillator, a transformer responsive to the oscillator for stepping up the pulses therefrom, a storage capacitor which is charged by the pulses from the transformer, and a trigger circuit which allows the energy stored in the capacitor to discharge and fire an explosive device. The energy stored in the capacitor is discharged through the explosive device by means ofa triggering circuit which may be operated automatically or manually. An example of a capacitor discharge type blasting machine of the aforementioned type, with which this invention may be used, may be found in U.S. Pat. No. 3,704,393 entitled Capacitive Discharge Type Blasting Machine to F. J. Digney et al., issued Nov. 28, I972.

The use of portable battery type blasting machines to initiate large blasting rounds, in preference to direct use ofcommereial power lines, as a source of electrical current, is well recognized, especially for underground blasting operations in tunnels and mines that employ delay electric blasting caps. Employment of capacitive discharge type blasting machines to initiate electric blasting caps, including both instantaneous and delay electric blasting caps, is especially well known, and some capacitive discharge blasting machines have been provided that initiate relatively large numbers of electrical blasting caps in a single blasting round. The number of electric blasting caps that can be initiated in a single round by a given blasting machine depends in part on the way in which the electric blasting caps are connected to the blasting machine. It is well known in the blasting art that numbers of electric caps can be initiated from a given power source in a single blast by arranging the caps in series or in parallel. The relative simplicity of making parallel firing circuit hook-ups with many caps in the round have created demands for dependable means of firing all the electric blasting caps that are connected in the firing circuit.

In certain blasting operations such as those performed in tunnels and shaft mining, it is generally desirable to connect as many as 150 blasting caps together in a parallel circuit, principally because such a circuit permits rapid connection of the blasting caps with minimal possibility of error. However, to insure that all the blasting caps are fired, the blasting machine must always deliver a given minumum energy each time it is fired; otherwise, all of the blasting caps may not be fired. Experience has shown that blasting machines occasionally do not provide all the power they are supposed to, thereby failing to detonate all the blasting caps they are supposed to.

SUMMARY OF THE lNVENTlON This invention provides an apparatus for determining that the energy discharged from the output ofa blasting machine is above a predetermined value and therefore the blaster discharges sufficient energy to detonate a predetermined number of electro-explosive devices.

The invention is an apparatus for testing the rated en ergy of a blasting machine characterized by the fact that it is connectable to receive the output energy from a blasting machine I and transmit the energy to a translator 2 to provide a signal, which is related to a predetermined acceptable energy level. The comparator 6 then provides indication 7 as to whether or not the energy discharged from the blasting machine 1 into the tester is above a predetermined acceptable amount. The tester circuitry is further characterized by the fact that it is capable of simulating a load of series connected or parallel connected blasting caps and that the output of the reference signal generator 3 is a pulse 52 having a predetermined magnitude and duration, that is compared by the comparator 6 to the output of the signal generator 2, which is a non-pulse type signal. the

magnitude of which varies with respect to time.

In one embodiment ofthe invention, the tester, used in combination with a blasting machine I of the type that discharges energy stored in a capacitor to initiate at least one electro-explosive device, comprises: a first circuit 201-214 for receiving the energy discharged from said blasting machine and producing a first signal B, the magnitude of which varies with respect to time, and which is related to the amount of energy discharged by said blasting machine', a second circuit 401-413, 501-514 for generating a reference signal A which is related to predetermined amount of energy, the circuit for generating a reference signal including a trigger circuit 401-413, responsive to the receipt of the energy received from the blasting machine 1, for generating a trigger pulse upon receipt of the blasting machine output energy, and a monostable multivibrator 501-514 for producing an output signal A in response to the trigger circuit pulse; a third circuit 601-609 for comparing the reference signal A to said first signal 8 and generating a third signal C when the magnitude of the first signal B exceeds the magnitude of the reference signal A during the presence T2 of said reference signal A; and a fourth circuit 710-729 responsive to said third signal C for indicating the presence of the third signal C whereby the indicating circuit gives an indication GO that the output energy received from said blasting machine is above a predetermined amount and therefore the blasting may be employed to detonate its rated number of blasting caps.

Accordingly, it is an object of this invention to provide an apparatus for determining whether or not the energy produced by the output of a blasting machine is at or above an acceptable level,

It is another object of this invention to prevent the application of energy to a plurality of electrically connected electro-explosive devices or the like when there is insufficient energy available to detonate all the devices.

It is still another object of this invention to provide the operator of a blasting machine with a device that allows him to test, rather easily. the amounts of energy available in his blasting machine.

It is a further object of this invention to provide a device which senses the total output energy of a blasting machine rather than the voltage level at the output ofa blasting machine.

The above and other objects and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which form a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a block diagram of a system incorporating the principles ofthis invention for evaluating the operational capabilities of a blasting machine.

FIG. 2 is a schematic diagram ofa preferred embodiment of the circuitry for an energy tester that accomplishes the principles of this invention.

FIG. 3 illustrates the relative magnitude and durations and shapes of the wave forms at various points within the monostahle multivibrator illustrated in FIG. 2.

FIG. 4 illustrates the signals being supplied to the comparator.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings, FIG. 1 illustrates a block diagram of a blasting machine 1 which is used in combination with the energy testing device embodying the principles of this invention. The energy testing device includes a reference signal generator 3 and a translator or signal generator 2 which supply signals to a comparator 6. The comparator 6 compares the received signals and provides an output signal that visually indicates *GO or "NO G0. The reference signal generator 3, which is related to an acceptable energy level, includes a trigger circuit 4, which is responsive to the discharge of energy from the blasting machine and which triggers a monostable multivibrator 5 that pro vides a pulse of fixed magnitude and duration that corresponds to a predetermined amount of energy. The output of the reference signal generator 3 is a pulse type signal, the magnitude of which is substantially constant with respect to time and is represented by the letter A. The signal generator 2, which is related to the amount of energy discharged from the blasting machine, is actuated simultaneously with the trigger circuit 4 upon the discharge of energy from the blasting machine 1. The output of the signal generator 2 is a signal that varies in magnitude with respect to time and is represented by the letter B. The comparator 6 receives signal A from the reference signal generator 3 and signal B from the signal generator 2 and compares them. The comparator 6 provides a signal C when the first signal B is equal to or exceeds the reference signal A at anytime during the presence of the reference signal A. The comparator 6 also provides a second signal D when the reference signal A is greater than the first signal B. Signal C actuates an indicating device GO that gives audio or visual indication that the blasting machine is putting out the amount of energy that it is supposed to. Signal D actuates an indicating device NO-GO that gives audio or visual indication that the blasting ma chine is not putting out sufficient energy.

FIG. 2 is a schematic diagram that illustrates a preferred embodiment of an apparatus that tests the amount of energy discharged from the output of a blasting machine. Portions of the schematic have been outlined with dotted lines which correspond to the functions illustrated in the block diagram shown in FIG. I.

In the schematic the blasting machine 1 is repre sented by a battery 100, a storage capacitor 101, which is triggered by a gaseous conductor 103, such as a spark gap discharge device. and a high impedance resistor 102. When the gaseous conductor 103 is triggered, the energy stored in capacitor 101 is discharged into the input terminals 8, 9 of the testing apparatus. The input terminals 8. 9 of the testing apparatus communicate with the reference signal generator 3 and the signal generator 2.

The signal generator 2, which is outlined by a broken line, elements 201-214, includes load resistors 201, 202, steering diode 203, current limiting resistors 205, 206, storage capacitors or energy level detecting capacitors 209, 210, and a resistor 207 to NULL the loading effects of leakage from the storage capacitors 209, 210. Zener diode 211 is used to protect a logic gate 601 which is the input of the comparator 6 from voltage transients. The two resistors 201, 202 are used to simulate different loads. i.e., blasting caps connected in series or in parallel. Switches 214, 204, 312 and 514 are two position switches. When the switches are in position A. the testing apparatus tests a blasting machine for the application of energy to series connected blasting caps. When the switches are in position B. the testing apparatus tests a blasting machine for the application of energy to parallel connected blasting caps or squibbs. The values of resistors 205, 206 and capacitors 209, 210, with their respective load resistors 201, 202 are chosen such that if the blasting machine capacitor 101 voltage and the trigger gap voltage 103 varies over normal tolerances for the same stored energy, (e.g.. 26 Joules), the voltage across capacitors 209 or 210 change less than 50 millivolts. The values of the resistors 201, 202, 205, 206 and capacitors 209, 210 of the signal generator having been chosen so that the voltage across capacitors 209 or 210 will attain the threshold level of the comparator gate 601 8.0 volts when 26 Joules of energy are discharged through the signal generator when the switches 214, 204, 212 and 514 are in position A or B. A change of l Joule or more in the energy discharged into the tester from the blasting machine will change the voltage generated across capacitor 209 or 210. It has been determined by design that for every 1 Joule change in energy discharged into the tester, the voltage change across capacitors 209 or 210 will change l00 millivolts. Obviously, the input gate 601 of the comparator 6 is sensitive enough to detect changes of I00 millivolts.

The reference signal generator 3. which is outlined by a broken line, comprises a trigger circuit, elements 401413 and a monostable multivibrator. elements 501-5l l. The trigger circuit 4, like the reference signal generator 2, is directly connected to the input 8, 9 of the testing apparatus. It is the function of the trigger circuit 4 to provide a trigger spike to the monostable multivibrator (S). The trigger circuit 4 uses a Darlington-type amplifier, transistors 406, 407 for an input stage which, with resistors 40], 404, has a very high input impedance, so that the energy discharged from the blasting machine into the tester is dissipated mostly in the reference signal generator 2. Therefore, the energy required to operate the trigger circuit 4 is negligible and substantially all the output energy of the blasting machine is directed to the reference signal generator 2. The output ofthe Darlington amplifier transistors 406, 407 is differentiated by capacitor 408 and resistors 410 to turn the output transistor 412 ON" causing a positive pulse T1, FIG. 3 at the collection of transistor 412. This positive output pulse is used to trigger the monostable multivibrator 5 ON" when it is transmitted through lead 51 to the input gate 501 of the monostable multivibrator 5. The primary purpose of the trigger circuit 4 is to provide an acceptable wave shape T1 to the input of the monostable multivibrator 5.

The monostable multivibrator 5 includes elements 501514 and test jack 50. The duration of the output pulse T2 of the monostable multivibrator 5 is independent of the duration of the input pulse Tl received from the trigger circuit 4 through lead 51. The magnitude and duration of the output pulses T2 are deter mined by capacitors 505 or 506 and the internal resistance of gate 503. To obtain a long output pulse, the capacitance of capacitors 50S and 506 is adjusted to be in the order of 0.6 mierofarads or less. Switch 514 serves the same purpose as switch 214 of the signal generator 2. Gates 501, 502, 503 and 507 are diode transistor logic elements with two inputs and four gates. When transistor 509 is OFF", capacitors 505 and 506 are charged through resistor 508. When transistor 509 is turned ON," capacitor 505 and 506 discharge. Transistor 509 is turned OFF very quickly when the leading edge of the trigger pulse T1 occurs at input 2 of gate 501. When the leading edge of the input signal pulse T1 turns the transistor $09 OFF," the base voltage of the transistor goes to minus V in minus Vbe which is minus 14.3 volts. The capacitors 505 or 506 then start to charge through resistor S08 and when the base to emitter voltage of the transistor 509 0.7 volts is reached, transistor 509 is turned "ON," concluding the output pulse T2. In this circuit, the duration of the output pulse T2 may be computed as 0.7 RC where R is resistor 508 and C is capacitor 505 or 506. The operational characteristics of the monostable multivibrator 5 may be seen by reffering to FIG. 3, explained later.

The voltage comparator 6, outlined by a broken line, elements 601 through 609 includes gates 601, 602, 603 and 604 which are diode transistor logic circuits with two inputs and four gates. Capacitor 605 is designed to eliminate transient spikes in the circuit caused by the discharge of the blasting machine into the testing apparatus. The comparator 6 is designed to provide an output signal C from gate 603 if the magnitude of the signal B applied to input 62 of gate 601 exceeds the magnitude of signal A at input 61 at anytime during pulse T2 and to provide an output signal D from gate 604 if the magnitude of the signal B applied to input 62 of gate 601 is less than the magnitude of signal A at input 61 at anytime during the presence of pulse T2 at input 61 of gate 601. An output signal D from gate 604 illuminates the "NO-GO" indicator 714 while an output signal C from gate 603 illuminates the GO" indicator 728.

The indicator circuit 7 elements 709-729, which is shown within a broken line, is a simple switching circuit using transistors 711, 722, 727 and resistors 709, 712, 720, 713, 721, 729. 723 in a switching arrangement to turn on indicator lights 714, 728 to give 60" and "NO-GO" signals in response to the output of the comparator 6.

FIG. 3 is a timing diagram that illustrates the wave forms at particular points A, B, D, E and F throughout the monostable multivibrator 5. The output of the monostable multivibrator 5 from gate 502 is transmitted through lead 61 to the input 61 of gate 601 of the comparator 6. The timing diagram illustrates that the output pulse T2 is initiated upon receipt of input pulse T1 and terminates when transistor 509 turns ON. See wave form F, which illustrates how the base of the transistor 509 goes from a negative potential to a posi tive potential to turn transistor 509 ON" by the charging action of capacitors S05 and 506. The duration T2 and magnitude M of the pulse formed by the monostable multivibrator 5 may be adjusted to any predetermined duration and magnitude. The magnitude of the pulse being representative of a selected energy level.

FIG. 4 illustrates the operational characteristics of comparator 6. Wave form A illustrates the pulse generated by the reference signal generator which is the output of the multivibrator 5 applied through lead 61 to the input of gate 601. Curves B and B illustrate the wave shapes introduced through lead 62 to the input of gate 601 and are representative of the voltage generated across capacitor 209 or 210. When the magnitude of the signal B applied to input 62 of gate 601 exceeds Curve B the magnitude of the reference signal A applied to the input 61 of gate 601 for the duration T2, the comparator provides a signal C that turns GO lamp 728 ON. However, when the magnitude of signal B applied to input 62 of gate 601 does not exceed Curve B the magnitude of the reference signal A applied to lead 61 of gate 602 at anytime during the duration T2 of the signal A, a signal is generated by the comparator that turns NO-GO" indicator 714 ON. In this sense, the comparator 6 may be considered a threshold detector since it supplies an output signal when a predetermined threshold voltage is exceeded.

OPERATION Referring now to the FIGURES, the apparatus for testing the acceptability of the output energy level of a blasting machine, operates as follows: The capacitor 101 of the blasting machine 1 is charged to its full value by the battery and connected to the inputs 8 and 9 of the tester. Trigger tube 103 is triggered to allow the energy in capacitor 101 to discharge into the testing apparatus. Assuming that the load to be tested is a plurality of series connected blasting caps, the switches 214, 204, 212 and 514 are placed in position A. Upon discharge of the energy from the storage capacitor 101, trigger circuit 4 is triggered, supplying a shaped wave form to monostable multivibrator 5 which in turn applies a reference signal A to the input 61 of gate 601 of comparator 6. The high input impedance of the trigger circuit 4 causes most of the energy from the storage capacitor 101 to be dissipated in the signal generator circuit 2. Simultaneously with the triggering of the trigger circuit 4, the signal generator 2 receives most of the energy from capacitor 101 and begins to charge capacitor 209 which in turn applies a signal B, the magnitude of which varies with respect to time, to the other input 62 of the gate 601 of the comparator 6. The magnitude and duration of signal A supplied to input 61 is related to a predetermined amount of energy and when signal A is exceeded by a signal B generated by the signal generator 2 it is known that the energy discharged by capacitor 101 exceeded that predetermined value. The signals from the monostable multivibrator 5 and the signal generator 2 are calibrated by supplying known amount of energies to the circuit. Upon receipt of the two signals A and B through input signals 61, 62 the comparator 6 supplies signals to the indicator circuitry 7. Referring now to FIGS. 1 and 4, it can be seen that 7 the comparator 6 applies a signal C to the indicator circuitry 7 to illuminate the indicator 728 when the magnitude of signal A from the reference generator drops below the magnitude of signal B from the signal generator Curve B. FIG. 4. Conversely, the comparator 6 provides a signal D to the "NO-GO" indicator 714 of the indicator circuitry 7 when the magnitude of the reference signal A from the monostablc multivibrator remains greater than the magnitude of signal 8 from the signal generator 2 Curve B, FIG. 4. Referring briefly to FIG. 4, it is to be noted that Curve B. which exceeds the magnitude of signal A during the time T2, causes the comparator 6 to generate a signal C which gives a GO indication, and further that Curve B is a signal. the magnitude of which does not exceed the magnitude of signal A during the time period T2 and therefore the comparator 6 generates a signal D, giving a "NO-GO indication.

While a preferred embodiment of the invention has been disclosed. it will be apparent to those skilled in the art. that changes may be made to the invention as set forth in the appended claims and, in some instances. certain features of the invention may be used to advantage without corresponding use of other features. For example. it is to be noted that a signal could be the presence or absence of a voltage depending on the system approach used. Further. the tester and appropriate switching circuitry could be permanently connected to the blasting machie circuitry to render the blasting machine inoperable if it were not operating properly. Accordingly. it is intended that the illustrative and de scriptive materials herein be used to illustrate the principles of the invention and not to limit the scope thereof.

Having described the invention, what is claimed is:

I. An apparatus for determining that the output energy supplied by a blasting machine, which discharges a single pulse ofjoules of energy to initiate electro-explosive devices. is above a predetermined amount. the apparatus comprising:

8 means for receiving the joules ofenergy of the single output pulse from said blasting machine and for producing a first signal which is related to the amount of energy of said blasting machine energy pulse. said first signal increasing in magnitude with respect to time;

means for generating a reference signal which is re lated to a predetermined amount of energy, said reference signal having a predetermined magnitude and predetermined duration. said means for generating a reference signal including a trigger circuit responsive to the receipt of the single output energy pulse from said blasting machine. said trigger circuit having an input resistance greater than l million ohms. means for generating a trigger pulse upon receipt of said blasting machine output energy pulse and a monostable multivibrator. having input means for receiving said trigger circuit pulse and output means for producing a pulse having a fixed magnitude in response to said trigger circuit pulse;

means for comparing said reference signal to said first signal and generating a third signal when the magnitude of the first signal exceeds the magnitude of the reference signal at any time during the presence of said reference signal; and

means responsive to said third signal for indicating the presence of said third signal, whereby said indicating means further indicates that the output energy from said blasting machine is not less than said predetermined energy.

2. The combination as recited in claim I wherein said energy receiving means includes means for dissipating substantially all of said energy received from said blasting machine.

3. The combination as recited in claim 1 wherein said energy dissipating means a resistor having a resistance at least three decades less than the input resistance of said trigger circuit.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3,922,604

DATED I November 25, 19,75

INVENTOR(5) 1 Kaushik H. Thakore it is certified that error appears in the ab0ve-identified patent and that said Letters Patent are hereby corrected as shown below:

Coiumn 5, tine 1, change "coiiection" to --coiiector--.

Column 5, h'ne 38, change "reffering" to referring Column 7, tine 29, change "machie" to -mach1'ne-.

Signed and Scaled this sixteenth D a y 0f March 1 9 76 [SEAL] A nest:

RUTH C. MASON Commissioner nfParems and Trademarks Column 8, line 37, after" the word "means" insert the word --1'nc1udes-. 

1. An apparatus for determining that the output energy supplied by a blasting machine, which discharges a single pulse of joules of energy to initiate electro-explosive devices, is above a predetermined amount, the apparatus comprising: means for receiving the joules of energy of the single output pulse from said blasting machine and for producing a first signal which is related to the amount of energy of said blasting machine energy pulse, said first signal increasing in magnitude with respect to time; means for generating a reference signal which is related to a predetermined amount of energy, said reference signal having a predetermined magnitude and predetermined duration, said means for generating a reference signal including a trigger circuit responsive to the receipt of the single output energy pulse from said blasting machine, said trigger circuit having an input resistance greater than 1 million ohms, means for generating a trigger pulse upon receipt of said blasting machine output energy pulse and a monostable multivibrator, having input means for receiving said trigger circuit pulse and output means for producing a pulse having a fixed magnitude in response to said trigger circuit pulse; means for comparing said reference signal to said first signal and generating a third signal when the magnitude of the first signal exceeds the magnitude of the reference signal at any time during the presence of said reference signal; and means responsive to said third signal for indicating the presence of said third signal, whereby said indicating means further indicates that the output energy from said blasting machine is not less than said predetermined energy.
 2. The combination as recited in claim 1 wherein said energy receiving means includes means for dissipating substantially all of said energy received from said blasting machine.
 3. The combination as recited in claim 1 wherein said energy dissipating means a resistor having a resistance at least three decades less than the input resistance of said trigger circuit. 